The present invention relates in general to automotive passive restraint systems, and more particularly to a control circuit for a motorized passive restraint system.
The passive restraint system in a motor vehicle is responsible for providing automatic seatbelt protection to the vehicle occupants. The operation of the system is defined according to certain conditions such as the open or closed position of a door and the occurrence of certain events, such as the turning on of the vehicle ignition switch. As required, a torso belt of the passive restraint system will travel along a track from a forward position to a rearward position to secure an occupant. Other conditions and events will cause the torso belt to travel to the forward position to allow an occupant to enter or leave the vehicle.
In addition to the torso belt, a manual lap belt is provided for securing about the hips of the occupant. The lap belt is pulled out from a retractor and latches with a buckle. A sensor in the buckle provides a signal indicating whether the lap belt is engaged so that a warning or reminder signal can be given to an occupant.
The torso belt travels by means of a motor-driven carrier riding in a track along the door frame. As the belt carrier moves from the "A" pillar at the forward position toward the "B" pillar at the rearward position, the torso belt spools out of a retractor usually located at the base of the vehicle seat at the opposite side of the occupant from the door. The unspooling of the torso belt provides sufficient belt length to extend from the retractor, around the vehicle occupant, and to the rearward position of the belt carrier at the "B" pillar.
The belt carrier is driven by a reversible electric motor through a drivebelt which interconnects the belt carrier and the motor. A control circuit actuates the motor based on the above-mentioned conditions which are determined by signals from a plurality of sensors. The sensor signals are evaluated by logic circuitry which control when and in which direction the reversible motor is actuated.
One of the variables used in prior art passive belt systems to decide whether to locate a belt in the forward or rearward position is the open or closed state of the door corresponding to that belt. For example, when the door is opened the belt will move to the forward position (except during a crash when an inertia switch prevents operation of the reversible motor). By locating the belt in the forward position, the driver or passenger can enter or exit the vehicle independent of the on or off state of the ignition.
For safety reasons, the vehicle doors should not normally be opened while the vehicle is in motion. A problem arises in the prior art passive belt system when it becomes necessary to open a door while in motion, such as during the backing-up of the vehicle near an obstacle or with an obscured (e.g., fogged or frosted) rear window. When the occupant opens the door and leans out of the vehicle, the torso belt moves forward even though the occupant has no intention of exiting.